8 Tin American Geologist. July, i s, .i: 
Mexico, where they had been collected on the return from the 
Colorado river expedition, but also at many localities west- 
ward beyond Santa Fe\ A discovery of curious interest in 
view of the discussions had between 1ST-") and 1881, was that 
of the tubereulate Halymenites in the Lower Cretaceous (Da- 
kota) sandstone, a form which in eastern Colorado is diag- 
nostic of the Fox Hills group. 
Four volumes upon the geology of Ohio were published 
during the period in which Dr. Newberry was director of the 
second geological survey of that state: his contributions to 
these were of great importance. Prior to the organization of 
the survey, he had worked out the section of the Lower Coal 
Measures, had discussed the petroleum of the eastern portion 
and h;id presented a synoptical view of the surface geology, 
besides publishing a sketch of the geology and a geological 
map of the state inWalling's Atlas of Ohio. After the organ- 
ization of the survey, his studies were confined to the Coal 
Measures and to the surface geology, each of which received 
careful attention even in the preliminary or annual reports. 
Volume ii of the final reports contains a chapter of eighty 
pages on surface geology, which, beyond all doubt, was 
the most careful and detailed presentation of that subject of- 
fered in this country up to that time. The basins of the great 
lakes are regarded as due to enlargement of pre-glacial valleys 
by glacial erosion, a doctrine presented long before by the 
author, but here enforced; thecausesof the climate of the ice- 
period are sought for and the various explanations and theories 
are tested; the nature and the relations of the lake ridges, dis- 
covered long before by the New York geologists but studied 
more carefully by Gilbert and N. H. Winchell, are examined, 
especially in the light of the studies by those geologists and 
of Dr. Newberry himself; the known facts respecting pre- 
glacial drainage are grouped: and the drift deposits of Ohio 
are described in detail. 
The same volume contains a long chapter upon the Carbon- 
iferous, in which are discussed some matters which could not 
be determined finally at that time. The coal beds are 
grouped and correlations made between different portions 
of the state, as well as of adjoining states. Very largely 
the grouping, in so far as it refers to the state of Ohio, re- 
